Connected: An Internet Encyclopedia
RFC 822 - 3.4.6. BRACKETING CHARACTERS

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### 3.4.6. BRACKETING CHARACTERS

There is one type of bracket which must occur in matched pairs and may have pairs nested within each other:

- Parentheses ("(" and ")") are used to indicate comments.

There are three types of brackets which must occur in matched pairs, and which may NOT be nested:

- Colon/semi-colon (":" and ";") are used in address specifications to indicate that the included list of addresses are to be treated as a group.

- Angle brackets ("<" and ">") are generally used to indicate the presence of a one machine-usable reference (e.g., delimiting mailboxes), possibly including source-routing to the machine.

- Square brackets ("[" and "]") are used to indicate the presence of a domain-literal, which the appropriate name-domain is to use directly, bypassing normal name-resolution mechanisms.

Next: 3.4.7. CASE INDEPENDENCE

Connected: An Internet Encyclopedia
RFC 822 - 3.4.6. BRACKETING CHARACTERS